Better attempt at an appengine wrapper.

go/src/infra/gae/libs/wrapper/featurebreaker_test.go

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package wrapper
+
+import (
+        "fmt"
+        "testing"
+
+        . "github.com/smartystreets/goconvey/convey"
+)
+
+type foo struct {
+        *BrokenFeatures

[M-A Ruel, 2015/05/25 17:14:51]

So this way you could embed the struct, not a pointer.

[iannucci, 2015/05/26 18:25:06]

I won't be able to initialize the map on-demand then, will I?

[M-A Ruel, 2015/05/27 00:27:10]

Yes, since you need to grab the lock in each method anyway.

+}
+
+func (f *foo) Foo() (string, error) {
+        err := f.IsBroken()
+        if err != nil {
+                return "", err
+        }
+        return "foo", nil
+}
+
+func (f *foo) Bar() (string, error) {
+        err := f.IsBroken()
+        if err != nil {
+                return "", err
+        }
+        return "bar", nil
+}
+
+type override struct {
+        *BrokenFeatures
+        totallyRekt bool
+}
+
+func (o *override) IsBroken() error {
+        if o.totallyRekt {
+                return fmt.Errorf("totallyRekt")
+        }
+        return o.BrokenFeatures.IsBroken()
+}
+
+func (o *override) Foo() error {
+        return o.IsBroken()
+}
+
+func TestTestable(t *testing.T) {
+        e := fmt.Errorf("sup")
+        f := foo{NewBrokenFeatures(e)}
+
+        Convey("Testable", t, func() {
+                Convey("can break functions", func() {
+                        s, err := f.Foo()
+                        So(s, ShouldEqual, "foo")
+                        So(err, ShouldBeNil)
+
+                        f.SetBrokenFeatures("Foo")
+                        _, err = f.Foo()
+                        So(err, ShouldEqual, e)
+
+                        Convey("and unbreak them", func() {
+                                f.UnsetBrokenFeatures("Foo")
+                                s, err = f.Foo()
+                                So(s, ShouldEqual, "foo")
+                                So(err, ShouldBeNil)
+                        })
+
+                        Convey("and breaking features doesn't break unrelated ones", func() {
+                                s, err := f.Bar()
+                                So(s, ShouldEqual, "bar")
+                                So(err, ShouldBeNil)
+                        })
+                })
+
+                Convey("Can override IsBroken too", func() {
+                        o := &override{NewBrokenFeatures(e), false}
+                        Convey("Can break functions as normal", func() {
+                                o.SetBrokenFeatures("Foo")
+                                So(o.Foo(), ShouldEqual, e)
+
+                                Convey("but can also break them in a user defined way", func() {
+                                        o.totallyRekt = true
+                                        So(o.Foo().Error(), ShouldContainSubstring, "totallyRekt")
+                                })
+                        })
+                })
+        })
+}